In the construction of gas-fired furnaces it is conventional to weld a pair of clam shells together to form a heat exchanger section and to incorporate at least one such section in the furnace. An opening is provided in the lower or pouch section of the heat exchange unit for insertion of a gas burner so that the section can be fired up to a predetermined capacity, frequently of the order of 25,000 B.T.U. per hour. An opening is also provided in the upper section of each heat exchange unit to permit collection and discharge of the flue gases produced by the gas burner. To the front of the heat exchanger there is generally secured a pouch plate over the pouch area and a front partition plate over the upper section of the heat exchanger. The combination of the pouch plate and front partition plate is then usually sealed to the sides of the furnace in order to isolate the air being heated by the heat exchanger sections in the rear of the furnace from the furnace controls located in the front. Once such gas-fired furnace is the "COMFORTMAKER" furnace manufactured by The Singer Company.
It has been customary in the art of gas-fired furnace manufacture to weld the pouch plate and front partition plate to the heat exchanger. This technique, however, is costly and the resultant structure is susceptible to cracking when subjected to expansion and contraction stresses which develop during the heat and off cycles of the furnace. One expedient resorted to in an attempt to overcome such disadvantages has been to provide mating flanges on the heat exchanger outlets and on the pouch and front partition plates. The mating flanges are then secured together by fastening means such as screws. However, assembly of the completed unit by this alternate technique is time-consuming and frequently results in distortion of the component parts. Also, component elements of the assembly tend to work loose when subjected to extend periods of expansion and contraction cycles.